The prior art includes several references that teach the use of padding in the soles of shoes. U.S. Pat. No. 2,468,887, issued to Malouf, teaches that a fallen metatarsal arch, which occurs when the second, third and fourth metatarsal bones are unnaturally depressed, gives rise to fatigue cramps and pain. This reference remedies the fallen metatarsal arch by inserting a cushion in the insoles or innersoles of shoes to support the second through fourth metatarsals. U.S Pat. Nos. 2,613,456 and 2,613,455, issued to Amico, also teach supporting with cushions unnaturally disposed foot bones. U.S. Pat. No. 3,099,267, issued to Cherniak, discloses a transverse support attached to the sock lining of a shoe for the purpose of supporting the metatarsal bones in shifting weight backwardly of the metatarsal heads. Several references (U.S. Pat. No. 1,867,431, issued to Wood; U.S. Pat. No. 2,366,096 issued to Gerber; U.S. Pat. No. 2,404,731, issued to Johnson; U.S. Pat. No. 2,486,653 issued to Hukill; U.S. Pat. No. 2,760,281, issued to Cosin; and U.S. Pat. No. 4,266,350 issued to Laux; and German patent document 2,458,674 ) disclose insoles having a top thin layer of leather and a thin bottom layer of resilient material with soft cushioning patent material placed between these two layers to form a raised cushion under the metatarsal region of the foot. U.S. Pat. No. 4,463,505, issued to Duclos, discloses an orthotic element attached to a shoe above the midsole including a raised metatarsal support that rises gradually towards the middle. U.S. Pat. No. 4,739,765, issued to Sydor et al., discloses an arch support including a removable, bendable and flexible metatarsal support inserts; metatarsal inserts of different height may be used for different activities.
U.S. Pat. No. 4,364,188, issued to Turner et al., discloses an outer sole and midsole structure designed in order to lessen the tendency of the shoe to overpronate. This reference discloses a midsole made of 35 durometer material with a forefoot cushion insert located under the metatarsal area of the foot, made of a lower durometer material (25). This reference teaches nothing with regard to lessening the likelihood of stress fractures in the metatarsals. French patent document No. 2,522,482 discloses a midsole having a first layer and forefoot and heel cushion inserts made of materials of varying hardness.